To prevent pollution and improve environment, a filter or a catalyst is applied to the treatment of an exhaust gas, and a honeycomb structure is frequently used as the filter itself for the treatment of the exhaust gas or a catalyst carrier. To collect and remove, for example, a particulate matter (PM, detected as three components of organic solvent soluble components, soot and sulfates) included in the exhaust gas from a diesel engine or the like, a diesel particulate filter (DPF) is incorporated and used in an exhaust system of the diesel engine or the like, and the honeycomb structure is used in this DPF.
In a case where the honeycomb structure is used as the DPF, it is to be noted that when the PM is collected and removed (during use) and when the PM deposited in the filter is burnt and removed to suppress the increase of a pressure drop due to the PM deposited in the filter with an elapse of time (during regeneration), a temperature rise easily becomes uneven, and a defect such as a crack is generated by a thermal stress sometimes. Especially in recent years, the DPF has been enlarged, and hence the thermal stress generated during the use and during the regeneration has increased more remarkably than before. The problems of the frequency and degree of the generation of the defect based on the thermal stress become more serious.
On the other hand, there is suggested a honeycomb structure having a structure in which a plurality of honeycomb segments are integrally adhered together by mutual adhesive faces via cement material layers. In such a honeycomb structure, the cement material layers perform a cushion-like function for suppressing thermal expansion, and hence the thermal stress is relaxed. Moreover, by the employment of a segment structure, a distance between a high temperature portion and a low temperature portion shortens, and a temperature gradient decreases. Therefore, the honeycomb structure having the segment structure has an advantage that a defect such as the crack is not easily generated. It is to be noted that examples of a prior document concerning the honeycomb structure having the segment structure include Patent Document 1.
Patent Document 1: JUM-A-2-117033
Patent Document 2: JP-A-1-145378
Patent Document 3: JP-A-7-204431
Patent Document 4: JP-A-2003-10616
Patent Document 5: JP-A-2003-117320